Quercetin
The onion antioxidant
- Type
- Plant flavonoid
- Typical amount
- Studies often use 500–1,000 mg per day, sometimes paired with vitamin C or bromelain for absorption.
- Best taken
- As directed on the formula label
- Caffeine
- None
- Main source
- It is found in onions, apples, capers, berries and leafy greens.
- Evidence level
- Moderately studied
Quercetin is a plant flavonoid with antioxidant and anti-inflammatory properties, found in many fruits and vegetables.
What is Quercetin?
Quercetin is a plant flavonoid with antioxidant and anti-inflammatory properties, found in many fruits and vegetables.
How Quercetin works in the body
It is studied for antioxidant effects and supporting metabolic and cardiovascular markers. In practical terms, this is the mechanism weight-loss formulas are counting on when they include quercetin.
What the research says about Quercetin and weight
Quercetin has a moderate body of research — some human trials plus supporting lab and animal work. The findings are promising but not definitive, and effect sizes are usually modest. Treat it as a reasonable supporting ingredient rather than a proven stand-alone solution.
How much Quercetin to take
Studies often use 500–1,000 mg per day, sometimes paired with vitamin C or bromelain for absorption. Always check the label of your specific formula — blends often contain less quercetin than studies use, especially inside proprietary blends that don’t disclose exact amounts.
Food sources and supplement forms
It is found in onions, apples, capers, berries and leafy greens.
Why Quercetin appears in weight-loss formulas
It appears in antioxidant and metabolic blends for its broad flavonoid research.
Safety, side effects and interactions
Generally well tolerated; very high doses may affect kidney function and interact with some medications. As with any supplement, if you are pregnant, breastfeeding, taking medication or managing a health condition, check with your doctor first.
How to choose a quality Quercetin supplement
When choosing a Quercetin product or a formula containing it, look for one that discloses the actual amount of quercetin (not just a proprietary-blend total), uses a recognizable form, and is made by a brand with third-party testing or GMP manufacturing. More isn’t always better — match the dose to what research and the label suggest, and be wary of products that hide quantities behind a blend.
The onion antioxidant
Onions are one of the richest dietary sources of quercetin, the flavonoid studied for inflammation and metabolism.
Common questions about Quercetin
What does Quercetin do for weight loss?
How much Quercetin should I take?
Is Quercetin safe?
How strong is the evidence for Quercetin?
Will Quercetin alone make me lose weight?
Does the dose in supplements match research?
Supplements with Quercetin
Formulas in the SourceLean directory that list Quercetin or a closely related form among their ingredients:
Related ingredients
Explore other compounds commonly found in weight-loss formulas:
Ingredient insights, explained
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